The present invention relates to an apparatus for arc-melting a cold iron source such as iron scrap and direct smelting reduction iron, etc. efficiently, and a melting method thereof.
Japanese unexamined patent publication No. 7-180975 discloses a scrap preheating device, wherein a shaft furnace is connected to an upper part of an arc furnace, and furthermore wherein one stage, or two stages or more of fire grates are attached to the shaft furnace, which is able to be opened or closed.
Japanese unexamined patent publication No. 7-332874 discloses a method, wherein there is arranged a first preheating chamber of rotary drum type which is horizontally placed, connected to an upper cover of a melting chamber of an arc-furnace; and wherein there is arranged a second preheating chamber which is connected to the first preheating chamber at the bottom. After a cold iron source is preheated by the exhaust gas generated from the melting chamber in the second preheating chamber, the preheated cold iron source is pushed into the first preheating chamber by a pusher and the preheated cold iron source is charged into the melting chamber via the first preheating chamber which is rotating.
Japanese examined patent publication No. 6-46145 discloses an apparatus, wherein a shaft type preheating chamber is directly connected to a melting chamber, and wherein a charge of cold iron source is charged into the melting chamber. As the charge is melted, a new charge of iron falls from the shaft type preheating chamber into the melting chamber while the cold iron source in the shaft type preheating chamber is being preheated by an exhaust gas. This continues until all of the cold iron source which is charged into the melting chamber and the shaft type preheating chamber is melted.
By means of the method and apparatus as described above, the high preheating effect can attain an electric power unit of 250 to 270 kWh/t. However, the above described Prior Art has the following problems.
According to JP7-180975 and JP7-332874, in order to charge the preheated cold iron resource into the melting furnace of the arc-furnace, a device for transporting the preheated cold iron source such as a pusher or a rotary drum is necessary. For this reason, the preheating temperature has a limitation when preheating by the exhaust gas from the melting chamber. That is to say, if a large amount of carbonaceous material such as coke and oxygen gas are blown into the melting chamber and the cold iron source is preheated by a large amount of the generated exhaust gas having a high temperature, the preheated temperature becomes high and the preheating effect is improved. However, in an apparatus, high exhaust gas temperatures causes problems such as heat deformation and fusion of the above described transporting device. Therefore, the exhaust gas temperature cannot be elevated.
On the contrary, according to JP6-46145, the shaft type preheating chamber is directly connected to the melting furnace Consequently, the above described device for transporting the cold iron source is not necessary and the above described problem does not occur. However, since each time the melted iron amount corresponding to one batch is melted, all of the cold iron source in the melting chamber is melted, the melted iron is poured off and none of melted iron is left in the preheating chamber. For this reason, a cold iron source for the next batch which is to be charged immediately thereafter cannot be preheated. Therefore, this method cannot be said to be sufficient, with respect to the effective use of exhaust gas.
It is an object of the present invention to provide an arc-melting apparatus for arc-melting a cold iron source which does not require a device for carrying and feeding the cold iron source to the preheating chamber. This apparatus can, also, preheat the cold iron source to be use in the following charge, and can melt the cold iron source with an extreme high efficiency unattainable conventional melting apparatus whereby use exhaust gas for preheat the scrap. More concretely speaking, an arc-melting apparatus for arc-melting cold iron source with electric power unit of less than 250 kWh/t can be provided. Furthermore, this apparatus provides a method for melting the cold iron source without using a large scaled apparatus, and for preventing harmful constituents from being generated. In order to attain the above-mentioned object, the present invention provides the following arc-melting apparatus for arc-melting cold iron source. That is to say,
The first invention is an arc-melting apparatus for arc-melting cold iron source comprising:
(a) a melting chamber for melting the cold iron source;
(b) a preheating shaft, which is directly connected to an upper part of one side of the melting furnace and into which is introduced the exhaust gas generated in the melting chamber, in order to preheat the cold iron source;
(c) an arc electrode for melting the cold iron source in the melting chamber;
(d) a cold iron source feed device for feeding the cold iron source to the preheating shaft so that the cold iron source is continuously maintained in the melting chamber and the preheating shaft;
(e) a tapping portion having a tapping hole, projecting into the melting chamber; and
(f) a tilting device for tilting the melting chamber on the side of the tapping portion to pour out the melted iron.
The second invention is an arc-melting apparatus for arc-melting cold iron source of the first invention, wherein being projected outward from the melting chamber the tapping portion having a tapping hole is positioned in a different direction from the direction toward which the cold iron source in the preheating shaft is fed to the melting chamber.
The third invention is an arc-melting apparatus for arc-melting cold iron source of the second invention, wherein the tapping portion is arranged at a right angle to the direction toward which the cold iron source is fed.
The fourth invention is an arc-melting apparatus for arc-melting cold iron source of the first invention or the second invention, which has a distance between the position of the preheating shaft adjacent to the melting chamber and the position of the tapping portion adjacent to the melting chamber, in order to make it possible to prevent the cold iron source from flowing over the tapping portion, when the melting chamber is tilted.
The fifth invention is an arc-melting equipment for arc-melting cold iron source of the fourth invention, wherein a distance between the position of the preheating shaft of the melting chamber and the position of the tapping position is longer than a horizontal distance of the base of the cold iron source resting in the melting chamber from the preheating shaft, to the melting chamber.
The sixth invention is an arc-melting apparatus for arc-melting cold iron source of any one of the first invention through the fifth invention, which has a travelling device for travelling the arc electrode following the molten iron which moves in the melting furnace.
The seventh invention is an arc-melting apparatus for arc-melting cold iron source of any one of the first invention through the sixth invention which has further another arc electrode which is placed at the tapping portion.
The eighth invention is an arc-melting apparatus for arc-melting cold iron source of any one of the first invention through the seventh invention which has a device for feeding oxygen gas at the lower position of the preheating shaft.
The ninth invention is an arc-melting apparatus for arc-melting cold iron source of any one of the first invention through the eighth invention which has a fuel feed device for feeding fuel together with oxygen gas to the cold iron source at the lower position of the preheating shaft of the melting furnace.
The tenth invention is an arc-melting apparatus for arc-melting cold iron source of any one of the first invention through the ninth invention which has a carbonaceous material feed device for feeding carbonaceous material to the melting furnace and an oxygen gas feed device for feeding oxygen gas to the melting chamber.
The eleventh invention is an arc-melting apparatus for arc-melting cold iron source of any one of the first invention through the tenth invention which has a device for elevating the temperature of the exhaust gas discharged from a post-burning chamber to a predetermined temperature or more, being equipped with the post-burning chamber which post-burns the residual of non-combusted gas generated in the melting furnace which has passed through the preheat chamber by feeding oxygen containing gas and with a cooling portion which cools an exhaust gas discharged from the post-burning chamber.
The twelfth invention is an arc-melting apparatus for arc-melting cold iron source of any one of the first invention through the eleventh invention which has an adsorbent feed device for feeding adsorbent to the exhaust gas which has been quickly cooled at the cooling portion.
The thirteenth invention is an arc-melting apparatus for arc-melting cold iron source of any one of the first invention through the twelfth invention. This invention has a device for burning one part or the whole of the incombustible gas generated from the melting chamber, by arranging single or plural steps of the gas introducing holes in a range from the surface of the bath in the melting chamber to the upper end of the cold iron source of the upper part of the preheating shaft and by feeding oxygen containing gas through the gas introducing holes to charge portion of the cold iron source.
The fourteenth invention is an arc-melting equipment for arc-melting cold iron source of any one of the first invention through the thirteenth invention. This invention has a gas feeding device for blowing an oxygen gas or an inert gas into the molten iron in the vicinity of boundary of the cold iron source in the melting chamber and the molten iron.
The fifteenth invention is an arc-melting method for arc-melting cold iron source comprising the steps of:
(1) introducing an exhaust gas generated in a melting chamber into a preheating chamber to preheat the cold iron source;
(2) melting the cold iron source by an arc electrode while the cold iron source is continuously or intermittently being fed to the preheating shaft so that the cold iron source may be continuously maintained in the preheating shaft and the melting chamber;
(3) tilting the melting furnace at the time when the molten iron is accumulated;
(4) heating the molten iron for a predetermined time by an arc electrode to elevate the temperature thereof; and
(5) tapping the molten iron in the state that the cold iron source may be continuously maintained in the preheating shaft and the melting chamber.
The sixteenth invention is an arc-melting method for arc-melting cold iron source of the fifteenth invention comprising the step of separating the molten iron and the cold iron source completely by tilting the melting chamber.
The seventeenth invention is an arc-melting method for arc-melting cold iron source of the fifteenth invention or the sixteenth invention comprising the step of blowing oxygen or the oxygen and fuel simultaneously onto the cold iron source at the lower position of the preheating shaft of the melting chamber.
The eighteenth invention is an arc-melting method for arc-melting cold iron source of any one of the fifteenth invention through the seventeenth invention comprising the step of blowing oxygen and carbonaceous material such as coke into the melting furnace.
The nineteenth invention is an arc-melting method for arc-melting cold iron source of any one of the fifteenth invention through the eighteenth invention wherein the cold iron source of 40% or more of one charge remains in the melting furnace and the preheating shaft during melting and at the time of tapping.
The twentieth invention is an arc-melting method for arc-melting cold iron source of any one of the seventeenth invention through the nineteenth invention, wherein the sum of the oxygen being blown into the lower part of the preheating shaft and the oxygen being blown into the melting furnace is 25 Nm3/ton or more.
The twenty-first invention is an arc-melting method for arc-melting cold iron source of any one of the fifteenth invention through the twentieth invention comprising the steps of:
melting the cold iron source in the melting furnace by feeding supplementary heat source such as arc heating and coke and oxygen to the melting furnace; feeding and post-burning oxygen containing gas to elevate an exhaust gas to a predetermined temperature or more without discharging to the outside of the system the residual of the non-combusted gas generated in the melting furnace which has passed through the preheat chamber; and thereafter cooling the exhaust gas continuously and quickly.
The twenty-second invention is an arc-melting method for arc-melting cold iron source of any one of the fifteenth invention through the twenty-first invention comprising the steps of:
melting the cold iron source in the melting furnace by feeding supplementary heat source such as arc heating and coke and oxygen to the melting furnace; arranging one or plural stages of gas introducing holes in a range from bath surface in the melting furnace to upper end of the cold iron source of upper part of the preheat shaft; and feeding oxygen containing gas from those gas introducing holes to the charge portion of the cold iron source to burn part or all of the non-combusted gas generated from the melting furnace.
The twenty-third invention is an arc-melting method for arc-melting cold iron source of the twenty-first invention or the twenty-second invention comprising the step of feeding adsorbent to the exhaust gas which has been quickly cooled at the cooling portion.
The twenty-fourth invention is an arc-melting method for arc-melting cold iron source of any one of the twenty-first invention through the twenty-third invention which is characterized in that the exhaust gas after the post-burning is 900xc2x0 C. or more.
The twenty-fifth invention is an arc-melting method for arc-melting cold iron source of any one of the fifteenth invention through the twentieth invention comprising the steps of:
melting the cold iron source in the melting furnace by feeding supplementary heat source such as arc heating and coke and oxygen to the melting furnace; arranging one or plural stages of gas introducing holes in a range from the surface of the bath in the melting furnace to upper end of the cold iron source of the upper part of the preheat shaft; feeding a predetermined amount of the oxygen containing gas from those gas introducing holes to the charge portion of the cold iron source to burn the non-combusted CO gas generated from the melting furnace; making the exhaust gas which is generated owing to burning of the non-combusted CO gas by the oxygen containing gas in the vicinity of the outlet of the preheating shaft have a predetermined temperature or more; and thereafter cooling the exhaust gas at the cooling portion which is connected to the upper part of the preheating shaft.
The twenty-sixth invention is an arc-melting method for arc-melting cold iron source of the twenty-fifth invention comprising the step of feeding adsorbent to the exhaust gas which has been quickly cooled at the cooling portion.
The twenty-seventh invention is an arc-melting method for arc-melting cold iron source of the twenty-fifth invention or the twenty-sixth invention, wherein the exhaust gas in the vicinity of the outlet of the preheating shaft is 900xc2x0 C. or more.
The twenty-eighth invention is an arc-melting method for arc-melting cold iron source of any one of the twenty-second invention through the twenty-seventh invention, wherein the whole blowing amount of the oxygen containing gas makes feed oxygen amount QIN which is calculated from oxygen concentration therein and flow rate therein have the following formula (A) with respect to oxygen amount Q (Nm3/min) which is blown in the melting furnace:
0.55Qxe2x89xa60.9Q . . . xe2x80x83xe2x80x83(A) 
The twenty-ninth invention is an arc-melting method for arc-melting cold iron source of any one of the fifteenth invention through the twenty-eighth invention comprising the steps of:
melting the cold iron source in the melting furnace by feeding supplementary heat source such as arc heating and coke and oxygen to the melting furnace; at the time of thereof introducing air into the melting furnace; and burning the non-combusted CO (Mainly CO) gas in the melting furnace so that 0.3xe2x89xa6ODxe2x89xa60.7 where CO2/(CO2+CO) is made to be OD.
The thirtieth invention is one wherein a melting method for melting the cold iron source uses the arc-melting equipment of any one of the first invention through the seventh invention.